Artificial eye system

ABSTRACT

The object of the invention is to provide an artificial eye system which has excellent usability and is practically feasible. In the present invention, an artificial eye system  1  is structured of an extracorporeal unit  2  which is mounted outside a user&#39;s body and an intracorporeal unit  3  which is mounted inside a user&#39;s eye. The extracorporeal unit  2  is provided with a visor  4  and a power supply unit  5 . The visor  4  includes a primary coil  10 , an image receiving element  6  which receives a picture image of an outside world, a light emitting element  7  which transmits an electric stimulus signal produced based on an image signal from the image receiving element  6 , and an eye-gaze point recognizing unit  13 . The intracorporeal unit  3  includes a secondary coil  12  which is electro-magnetically induced by the primary coil  10 , a light receiving element  14  which receives the electric stimulus signal from the light emitting element  7 , a signal processing circuit  16  which processes the electric stimulus signal received by the light receiving element  14 , and a plurality of electrodes  11  which transmits the electric stimulus signal processed by the signal processing circuit  16  to the retinal N.

TECHNICAL FIELD

[0001] The present invention relates to an artificial eye system.

BACKGROUND ART

[0002] Despite the recent advancement in medical technologies, aneffective cure for blindness has not been devised yet. Blindness is notlimited to a mere loss of a visual function but is a disease seriouslyaffecting the patient's mental life and social life. Therefore,technologies for curing blindness are acutely demanded.

[0003] One of the blindness cure technologies is implemented in anartificial eye system designed to replace the function of a diseasedpart such as the retina or the optic nerve with an artificial entity. Ingeneral, the artificial eye system comprises an extracorporeal imagereceiving element and a nerve stimulating electrode implanted in anintracorporeal region. Image information received by the image receivingelement is transmitted to the brain via the stimulating electrode.Therefore, at least an image information transmission system fortransmitting the image information and a power supply system forsupplying power to the electrode are needed.

[0004] However, the study of the artificial eye system has just started.Something, which is movable with a user (blind patient) and has theimage information transmission system and the power supply systemcombined appropriately, has not yet been available.

[0005] The present invention has been made in view of the abovecircumstances and has an object to provide an artificial eye systemwhich has excellent usability and is practically feasible.

DISCLOSURE OF INVENTION

[0006] In order to accomplish the above object, the present inventionhas the constituent features described below.

[0007] (1) According to one aspect, the present invention provides anartificial eye system in which stimulus signal producing means convertsan image signal, which represents an image of an outside world receivedby an image receiving element, into an electric stimulus signal, and theelectric stimulus signal is transmitted from an electrode attached to aretina, the system including: an extracorporeal unit which is mountedoutside a user's body; and an intracorporeal unit which is mountedinside the user's body, the extracorporeal unit including a visor and apower supply unit which supplies electricity to the visor, the visorincluding a primary coil, the image receiving element, and a lightemitting element which transmits the image signal from the imagereceiving element as an imaging signal, and the intracorporeal unitincluding: a secondary coil which is electro-magnetically induced by theprimary coil; a light receiving element which receives the imagingsignal from the light emitting element; a signal processing circuitwhich processes the imaging signal received by the light receivingelement; and an electrode unit which has a plurality of electrodes thattransmits the electric stimulus signal, which is processed by the signalprocessing circuit, to the retina.

[0008] The “visor” is an object to be mounted on the face in the samemanner as glasses are. The visor may have any shape.

[0009] The “light emitting element” is an element that transmits animage signal, for example, a light-emitting diode for emitting infrared,red, green, or blue radiation. Among them, the employment of theinfrared light emitting diode (for example, from 800 nm to 1000 nm) hasthe merits described below. Namely, {circle over (1)} since a human bodyis little affected and the transmittance of infrared light is high, anartificial eye system that is more reliable can be provided. {circleover (2)} The artificial eye system can be put to practical use withoutbeing legally restricted by the Radio Law or the like. {circle over (3)}The artificial eye system is basically effective within a range withinwhich light passes. {circle over (4)} The light emitting element and thelight receiving element can be manufactured at a low cost and compactly.

[0010] The “image signal” means a signal representing an image receivedby the image receiving element. Moreover, the “electric stimulus signal”is an electric signal to be transmitted from the electrodes to theretina. The image signal is converted into the electric stimulus signalby the stimulus signal producing means. This stimulus signal producingmeans may be included in either the extracorporeal unit or theintracorporeal unit according to an overall circuitry. In thisdescription, the “imaging signal” signifies either the image signal orthe electric stimulus signal.

[0011] The stimulus signal producing means includes either hardware (forexample, a dedicated circuit formed in a semiconductor device) orsoftware (more particularly, a computer and software). However, thestimulus signal producing means performs a relatively large number ofcalculations and therefore consumes a large amount of power.Consequently, the stimulus signal producing means is preferably includedin the extracorporeal unit. Moreover, if the stimulus signal producingmeans were included as hardware in the intracorporeal unit, there wouldbe difficulty in designing it compactly. Since the intracorporeal unitshould be designed as compactly as possible, the stimulus signalproducing means should be incorporated in the extracorporeal unit.

[0012] The “retina” includes retinal photoreceptor cells, retinalbipolar cells, and retinal ganglion cells. Preferably, the electricsignal is applied to the retinal bipolar cells or the retinal ganglioncells. Therefore, the electrodes are preferably disposed within theretina rather than being mounted on the retina.

[0013] According to the present invention set forth in (1), theartificial eye system can move together with a user (blind patient) andtherefore offers excellent usability. Moreover, the image signal istransferred while being carried by light. When the eyelids are closed,an image disappears. Compared with a case where an electromagneticinduction device is used to transfer an image signal, vision isperceived with a natural feeling.

[0014] (2) In the artificial eye system set forth in (1), the outerdiameter of the secondary coil ranges approximately 5 mm toapproximately 12 mm.

[0015] In this description, the range “from approx. 5 mm to approx. 12mm” defining the size of the intracorporeal unit is a range permissibleby the average diameters of the crystalline capsule and the ciliaryfurrow respectively, that is, the average diameters of approx. 7 mm andapprox. 10 mm. When the size of the intracorporeal unit ranges fromapprox. 5 mm to approx. 8 mm, it can be mounted in the crystallinecapsule. Moreover, when the size of the intracorporeal unit rangesapprox. 8 mm to approx. 12 mm, it can be mounted in the ciliary furrow.

[0016] According to the present invention set forth in (2), thesecondary coil can be mounted in the ciliary furrow or the crystallinecapsule. Therefore, compared with a case where the secondary coil isdisposed on the equatorial plane of the eyeball, the primary coil andthe secondary coil are located close to each other. This leads to animprovement in the efficiency of electromagnetic induction between thecoils.

[0017] (3) In the artificial eye system set forth in (1), the signalprocessing circuit is integrated together with the electrodes on asubstrate, and the outer diameters of the secondary coil and the lightreceiving element range from approx. 5 mm to approx. 12 mm.

[0018] The secondary coil and the light receiving element need not beintegrated with each other. However, when the secondary coil and thelight receiving element are integrated with each other, the ease ofhandling improves.

[0019] According to the present invention set forth in (3), thecomponents other than the signal processing circuit and the electrodes,that is, the secondary coil and the light receiving element may beimplanted in the ciliary furrow or the crystalline capsule.Consequently, compared with the case where the secondary coil and thelight receiving element are disposed in the eyeball, an implantation canbe achieved easily. Moreover, the damage to a user caused by theimplantation is limited.

[0020] (4) In the artificial system set forth in (4), the outerdiameters of the signal processing circuit, the secondary coil, and thelight receiving element range from approx. 5 mm to approx. 12 mm.

[0021] The signal processing circuit, the secondary coil, and the lightreceiving element need not always be integrated with one another.However, when they are integrated with one another, the ease of handlingimproves.

[0022] According to the present invention set forth in (4), thecomponents other than the electrodes, that is, the signal processingcircuit, the secondary coil, and the light receiving element can beimplanted in the ciliary furrow or the crystalline capsule. Therefore,compared with a case where the components are disposed in the eyeball,the implantation can be achieved easily. The damage to a user caused bythe implantation is limited.

[0023] (5) According to another aspect, the present invention providesan artificial eye system in which stimulus signal producing meansconverts an image signal, which represents an image of an outside worldreceived by an image receiving element, into an electric stimulussignal, and the electric stimulus signal is transmitted from anelectrode attached to a retina, the system including: an extracorporealunit which is mounted outside a user's body; and an intracorporeal unitwhich is mounted inside the user's body, the extracorporeal unitincluding a visor and a power supply unit which supplies electricity tothe visor, the visor including a power transmitter which transmitspower, the image receiving element, and an imaging signal transmitterwhich transmits the image signal from the image receiving element as animaging signal, and the intracorporeal unit including: a power receiverwhich receives the power from the power transmitter; an imaging signalreceiver which receives the imaging signal from the imaging signaltransmitter; a signal processing circuit which processes the imagingsignal received by the imaging signal receiver; an electrode unit whichhas a plurality of electrodes that transmits the electric stimulussignal processed by the signal processing circuit to the retina; and apower storage element which supplies the power to the electrodes and thesignal processing circuit.

[0024] The “power transmitter” and the “power receiver” are a pair ofunits that transmits or receives power to or from the intracorporealunit or the extracorporeal unit. The power transmitter and the powerreceiver are connected to each other according to, for example, a wiredmethod in which power lines are directly joined (in this case, the powerlines extending from the extracorporeal unit and the intracorporeal unithave connectors that are detachably attached to each other for betterusability), or a wireless method in which a primary coil (incorporatedin the extracorporeal unit) and a secondary coil (incorporated in theintracorporeal unit) are used to transmit power through electromagneticinduction. Needless to say, any other method those skilled in the artcan utilize can be adopted.

[0025] The “imaging signal transmitter” and the “imaging signalreceiver” are a pair of units that transmits or receives an image signalto or from the intracorporeal unit or the extracorporeal unit. Theimaging signal transmitter and the imaging signal receiver are connectedto each other according to, for example, a wired method in which signallines are directly joined (in this case, the signal lines extending fromthe extracorporeal unit and the intracorporeal unit have connectors thatare detachably attached to each other for better usability) or awireless method in which a primary coil (incorporated in theextracorporeal unit) and a secondary coil (incorporated in theintracorporeal unit) are used to transmit a signal throughelectromagnetic induction. Incidentally, the signal lines employed inthe wired method include electric lines and optical fibers. The wirelessmethod adopts not only electromagnetic induction but also a light signaltransmitting/receiving form.

[0026] The “power storage element” is a generic element capable ofstoring power, for example, a battery (a primary battery or a secondarybattery) or a capacitor. Moreover, the weight of the power storageelement ranges from approx. 0.5 g to approx. 2 g.

[0027] When a user wearing the artificial eye system moves his/her eyes,the secondary coils may tilt. Consequently, the efficiency inelectromagnetic induction between the primary and secondary coils maydeteriorate, and electromotive force induced in the secondary coil maydiminish. According to the present invention set forth in (5), even insuch a case, since power stored in the power storage element can beused, a stable image signal can be transmitted to the retina.

[0028] (6) According to another aspect, the present invention providesan artificial eye system in which stimulus signal producing meansconverts an image signal, which represents an image of an outside worldreceived by an image receiving element, into an electric stimulussignal, and the electric stimulus signal is transmitted from anelectrode attached to a retina, the system including: an extracorporealunit which is mounted outside a user's body; and an intracorporeal unitwhich is mounted inside the user's body, the extracorporeal unitincluding a visor and a power supply unit which supplies electricity tothe visor, the visor including a power transmitter which transmitspower, the image receiving element, an imaging signal transmitter whichtransmits the image signal from the image receiving element as animaging signal, and an eye-gaze point recognizing unit which recognizesan eye-gaze point, the intracorporeal unit including: a power receiverwhich receives the power from the power transmitter; an imaging signalreceiver which receives the imaging signal from the imaging signaltransmitter; a signal processing circuit which processes the imagingsignal received by the imaging signal receiver to produce the electricstimulus signal for stimulating the retina; and an electrode unit whichhas a plurality of electrodes that transmits the imaging signal, whichhas been processed by the signal processing circuit, to the retina, andthe electric stimulus signal representing information acquired in adirection of the eye-gaze point recognized by the eye-gaze pointrecognizing unit being transmitted from the electrodes to the retina.

[0029] The “eye-gaze point recognizing unit” recognizes the user'seye-gaze point. A concrete example is a unit that recognizes an eye-gazepoint on the basis of the movement of reflected light of lightirradiated to the cornea according to the fact that the radius ofcurvature of the cornea is smaller than those of the other parts of theeyeball (that is, the cornea projects more greatly than the other partsdo). Another unit that recognizes an eye-gaze point and can be adoptedutilizes the fact that the intensity of light reflected from the eye onthe light receiving element or the imaging element included in the visorlocated in front of the eyes changes along with a change in the ratio ofthe iris and the pupil to the sclera caused by the motion of theeyeball. Otherwise, an electro-oculogram (EOG), a video oculogram (VOG),or a search coil may be used to recognize an eye-gaze point.

[0030] When it says that “the electric stimulus signal representinginformation acquired in a direction of the eye-gaze point is transmittedfrom the electrodes to the retina,” it means that {circle over (1)} theimage receiving element is driven based on a direction recognized by theeye-gaze point recognizing unit. Otherwise, it means that: {circle over(2)} a visual field (an image receiving visual field) covered by theimage receiving element is set to be larger than a visual field (atransmitting visual field) whose image is transmitted from theelectrodes to the retina; and the transmitting visual field is definedwithin the image receiving visual field according to the direction ofthe eye-gaze point.

[0031] According to the present invention set forth in (6), when a usermoves his/her eye-gaze point, the user can sense an image in thedirection of the eye-gaze point. This results in an artificial eyesystem offering excellent usability.

[0032] (7) In the artificial eye system set forth in (6), the imagereceiving visual field whose image is represented by the image signalproduced by the image receiving element is set to be larger than thetransmitting visual field whose image is transmitted from the electrodesto the retina, and an image of a portion of the image receiving visualfield located in the direction of the eye-gaze point recognized by theeye-gaze point recognizing unit is transmitted as an image of thetransmitting visual field to the electrodes.

[0033] A circuit for defining the transmitting visual field within theimage receiving visual field may be incorporated in the extracorporealunit or the intracorporeal unit.

[0034] According to the present invention set forth in (7), an electricstimulus signal representing information of the transmitting visualfield smaller than the image receiving visual field is transmitted fromthe electrodes. According to one method {circle over (1)}, part of animage receiving signal is extracted as a signal representing thetransmitting visual field, and the part of the image receiving signalrepresenting the transmitting visual field is adopted as the electricstimulus signal. According to the other method {circle over (2)}, afterthe image receiving signal is adopted as a full electric stimulussignal, part of the image receiving signal representing the transmittingvisual field is adopted as the electric stimulus signal.

[0035] According to the present invention set forth in (7), thecomponent for changing images with the movement of an eye-gaze point isnot hardware (for example, a component for driving the image receivingelement) but software. This leads to a simplified overall configuration.

[0036] (8) In the artificial eye system set forth in (1) to (7), theelectrode unit has a plurality of pores that penetrates through theelectrode unit in a direction of a thickness.

[0037] The “pores” are holes that have the size permitting nutrition topass through the electrode unit.

[0038] According to the present invention set forth in (8), since theplurality of pores is bored in the electrode unit, nutrition can be fedfrom the cells of the sclera to the cells of the retina. The electrodeunit can therefore be implanted below the retina. Compared with a casewhere the electrode unit is mounted on the retina, the power of anoutput signal can be lowered. Consequently, even when the secondary coilis small and induced electromotive force is limited, an excellent imagesignal can be transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 shows the overall configuration of an artificial eye systemaccording to a present embodiment;

[0040]FIG. 2 is a perspective view schematically showing a wholeextracorporeal unit included in the artificial eye system;

[0041]FIG. 3 shows a visor seen in the direction of arrow A in FIG. 1;

[0042]FIG. 4 shows the operation of an eye-gaze point recognizing unit;

[0043]FIG. 5 shows the whole of an intracorporeal unit, (A) is a planview, and (B) is a cutaway side view of a secondary coil;

[0044]FIG. 6 shows a state before the intracorporeal unit is implantedin an eyeball;

[0045]FIG. 7 is a side sectional view showing the eyeball in which theintracorporeal unit has been implanted;

[0046]FIG. 8 shows the relationship between an image receiving visualfield and a transmitting visual field, (A) shows the image receivingvisual field, (B) shows the transmitting visual field, and (C) shows animage actually transmitted to electrodes;

[0047]FIG. 9 is a flowchart describing image signal processing to beperformed in the extracorporeal unit;

[0048]FIG. 10 is a flowchart describing imaging signal processing to beperformed in the intracorporeal unit;

[0049]FIG. 11 is a side sectional view showing a front device mounted inthe ciliary furrow according to another embodiment; and

[0050]FIG. 12 is a side sectional view showing the front device mountedin the ciliary furrow according to another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0051] Next, embodiments of the present invention will be describedbelow. The technological scope of the present invention is not limitedto the embodiments. Various application of the invention can beimplemented without departing from the scope of the invention. Moreover,the technological scope of the invention encompasses an equivalentscope.

[0052] Referring to FIG. 1 to FIG. 10, an embodiment of the presentinvention will be described below.

[0053] As shown in FIG. 1, an artificial eye system 1 in the presentembodiment is constructed of an extracorporeal unit 2 which is mountedoutside a user's body and an intracorporeal unit 3 which is mountedinside the user's body (specifically, in the eyeball).

[0054] The operation of the artificial eye system 1 will first brieflybe explained below. A visor 4 included in the extracorporeal unit 2 hasa TV camera 6 and eye-gaze point recognizing units 13. A signalcomponent of a signal received by the TV camera 6 which representsinformation of a direction recognized by the eye-gaze point recognizingunits 13 is extracted by a computer 9, whereby a transmission signal isproduced. The signal is transmitted to the intracorporeal unit 3 vialight emitting devices 7, and then processed appropriately. Theresultant signals are then transmitted to electrodes 11 implanted in aregion near the retina. Thus, each electric signal is applied to theremaining retinal bipolar cells or retinal ganglion cells (hereinafter,simply, the retina). Moreover, the extracorporeal unit 2 includes apower supply unit 5 that drives the computer 9. Primary coils 10 andsecondary coils 12 are incorporated in the extracorporeal unit 2 and theintracorporeal unit 3 respectively. Power is transmitted to theintracorporeal unit 3 owing to electromagnetic induction occurringbetween each pair of the coils 10 and the coils 12.

[0055] Next, the components will be detailed below. FIG. 2 schematicallyshows the whole extracorporeal unit 2. The extracorporeal unit 2 fallsbroadly into the visor 4 which a user wears in front of his/her eyes,and a processing unit 8 that includes the power supply unit 5 forsupplying power to the visor 4. These members 4 and 8 are connected toeach other through a wire W whereby electricity and signals aretransferred. At an upper part of the processing unit 8, the computer 9is located for supplying electricity, processing image data, andtransmitting a signal. The power supply unit 5 (secondary battery) islocated under the computer 9.

[0056] Moreover, the visor 4 includes the TV camera 6 serving as animage receiving element for receiving a picture image of an outsideworld, and the light emitting element 7 for transmitting an image signalsent from the TV camera 6 into the intracorporeal unit 2 (see FIG. 2 aswell as FIG. 3). In the present embodiment, a near infrared lightemitting diode is adopted as the light emitting element 7. As shown inFIG. 3, the primary coils 10 and the eye-gaze point recognizing units 13are provided on the back surface of the visor 4 (at two positions facingthe user's eyes). The primary coils 10 are electromagnetically coupledto the secondary coils 12 included in the intracorporeal unit 3 thatwill be described later.

[0057] In the present embodiment, a single TV camera 6 is provided inthe visor 4. The present invention is not limited thereto.Alternatively, two TV cameras may be arranged for the right and lefteyes.

[0058] Moreover, the eye-gaze point recognizing unit 13 includes a lightreceiving element that detects light emitted from the light emittingelement 7 and reflected from the eyeball. As shown in FIG. 4, incidentlight C emitted from the light emitting element 7 is reflected from eachof the surface D of the cornea, the bottom E of the cornea, the surfaceF of the crystalline lens, and the bottom G of the crystalline lens (P1to P4 in FIG. 4 denote light rays reflected from the surfaces andbottoms D to G). In the present embodiment, the light receiving elementreceives the light reflected from the surface D of the cornea (P1, afirst Purkinje image). The direction of the eye-gaze point is recognizedbased on the incident light C and reflected light P1.

[0059] The configuration of the intracorporeal unit 3 will be describedbelow, referring to FIG. 5. The intracorporeal unit 3 includes a frontunit 15 which is implanted in the anterior part of the eyeball, and anelectrode unit 19 composed of a plurality of electrodes 11 thattransmits an electric signal to the retina N. The members 15 and 19 areconnected through a cable 18. The front unit 15 includes the secondarycoil 12 that receives the power from the primary coil 10, the lightreceiving element 14 that receives the image signal from the lightemitting element 7, and an integrated circuit 16 provided with a signalprocessing circuit which processes the image signal received by thelight receiving element 14, and a demultiplexer. The light receivingelement 14 and the integrated circuit 16 have substantially the sameouter diameter. The secondary coil 12 has an outer diameter larger thanthe outer diameters of the light receiving element 14 and the integratedcircuit 16. The outer diameter of the secondary coil 12 ranges approx. 5mm to approx. 8 mm, and is equal to or slightly larger than the innerdiameter of an opening of the crystalline capsule H. Moreover, the lightreceiving element 14 and the integrated circuit 16 are concentricallyintegrated with each other on the back of the secondary coil 12 via aresin substrate 21.

[0060] In the present embodiment, the light receiving element 14 and theintegrated circuit 16 are concentrically integrated with each other onthe back of the secondary coil 12 via the resin substrate 21; but thepresent invention is not limited thereto as long as the light receivingelement 14 and the secondary coil 12 can be placed in the anterior partof the eye and integrated into the resin substrate 21. For example, theintegrated circuit 16 may be set on the back of the electrode unit 19.Moreover, the light receiving element 14 and the integrated circuit 16may be placed on the same side as the side of the substrate 21 on whichthe secondary coils 12 are placed. Moreover, the light receiving element14 and the integrated circuit 16 may not always be concentric to thesecondary coil 12. Furthermore, although the light receiving element 14and the integrated circuit 16 are separate elements in the presentembodiment, the present invention is not limited to this mode.Alternatively, the light receiving element 14 and the integrated circuit16 may be integrated with each other.

[0061] Moreover, the integrated circuit 16 includes a power supplycircuit 22 that converts an alternating current caused to flow by thesecondary coil 12 into a direct current, and a power storage element 17in which power is stored when power is abundant. The front unit 15 andthe electrodes 11 are connected to one another through the cable 18.

[0062] The electrode unit 19 is formed of a thin polymer member havingappropriate elasticity and being shaped substantially like a disk. Theplurality of electrodes 11 for transmitting an electric signal to theretina N is arranged in rows and columns, or in a matrix pattern, with apredetermined space between adjoining electrodes. The electrode unit 19has a plurality of pores 20 formed penetrating through the electrodeunit 19 in the direction of the thickness (for example, a laser may beused to bore the pores or a porous polymer may be adopted).Consequently, nutrition can pass through the electrode unit 19 (forbrevity's sake, part of the pores 20 alone is shown in FIG. 5).Moreover, when a polymer member having numerous apertures but not thethrough holes is employed, after the electrode unit 19 is placed on orunder the retina N, peripheral cells are expected to grow while invadinginto the apertures. The degree of adhesion between the electrode unit 16and retina N is expected to improve owing to the growth of theperipheral cells.

[0063] In order to implant the intracorporeal unit 3 in the eyes, asshown in FIG. 6, the sclera J of each eye in a region approx. 1.5 mmaway from the corneal annular margin B on the side of the cornea nearthe ear is resected by a length ranging from 7 mm to 8 mm. Thus, aninsertion port is created. The front unit 15, the electrode unit 19, andthe cable 18 are inserted into the eye through the insertion port.Moreover, after the crystalline lens is taken out, the front unit 15 isimplanted so that the external periphery of the second coil 12 will beheld with the muscle on the perimeter P of the opening of thecrystalline capsule H. Moreover, the cable 18 is implanted while beinglaid on the internal surface of the sclera J, and the electrode unit 19is placed inside the retina N.

[0064] Next, referring mainly to FIG. 8 to FIG. 10, the operation andeffect of the present embodiment having the foregoing components will bedescribed below.

[0065] Image information processing will first be summarized. The TVcamera 6 includes, for example, approx. one million pixel locations. Animage receiving visual field (that is, an area whose information isrepresented by an image signal produced by the TV camera 6) whose imageis received by the TV camera 6 is a range defined with an angle ranging,as shown in FIG. 8(A), from approx. 60° to approx. 80°. Incidentally,the number of electrodes 11 for transmitting an electric signal to theretina N ranges from about several tens of electrodes to severalthousands of electrodes at most according to the current technologicallevel. Almost all of image information received by the TV camera 6 istherefore not transmitted to the retina N. In the present embodiment,accordingly, the image receiving visual field of the TV camera 6 (FIG.8(A)) is set to be larger than the transmitting visual field (FIG. 8(B))whose image is transmitted from the electrodes 11 to the retina N. Awindow (transmission visual field) is defined in the image receivingvisual field according to the direction of the eye-gaze point recognizedby the eye-gaze point recognizing unit 13. An image signal representingthe image of the window is quantized (FIG. 8(C)), and transmitted fromthe electrodes 11 to the retina N.

[0066] In the present embodiment, the image receiving visual field whoseimage is received by the TV camera 6 is a range defined with an angleranging from approx. 60° to approx. 80°. The present invention is notlimited to this mode. Alternatively, a range defined with an angleranging, for example, from 60° to 180° will do.

[0067] Next, referring to FIG. 9, image signal processing to beperformed in the extracorporeal unit 2 will be described below.

[0068] The TV camera 6 included in the visor 4 receives an image of aforward image receiving visual field (S100 in FIG. 9; FIG. 8(A)).

[0069] On the other hand, the eye-gaze point recognizing units 13 andcomputer 9 detect the direction of a user's eye-gaze point (S110). Animage signal representing an image of a window having a predeterminedsize in the direction of the eye-gaze point is extracted from an imagesignal representing the image of the whole image receiving visual field(S120; FIG. 8(B)). The image signal representing the image of the windowrepresents a large amount of information for the number of electrodes11. Therefore, the image signal representing the image of the window isquantized in order to produce a signal suitable for the number ofelectrodes 11 (S130).

[0070] Thereafter, stimulus signal producing software is used to producean electrode stimulus signal from the quantized image signal (S140).Furthermore, the electrode stimulus signal is modulated and transmittedfrom the light emitting elements 7 (S150). For the modulation of theelectrode stimulus signal, for example, a pulse frequency, a pulsewidth, a pulse amplitude, and the number of pulses can be used asparameters for modulation.

[0071] Next, referring to FIG. 10, image signal processing to beperformed in the intracorporeal unit 3 will be described. First, thelight receiving elements 14 receives the electrode stimulus signal fromthe light emitting elements 7 (S200). Thereafter, the signal processingcircuits included in the integrated circuit 16 demodulate the respectiveelectric stimulus signals so as to produce pulse signals for stimulatingthe electrodes 11 (S210).

[0072] Next, the pulse signals are transmitted to the electrodes 11 viathe demultiplexers (S220). With the pulse signals sent from theelectrodes 11, electric signals are applied to the remaining retinas Nof the eyes.

[0073] As mentioned above, according to the present embodiment, theartificial eye system 1 is movable together with a user and thereforeprovides excellent usability. Moreover, the image signal is transmittedvia the light emitting elements 7 and light receiving elements 14 whilebeing carried by light. Therefore, when the eyelids are closed, an imagedisappears. Consequently, compared with a case where an image signal istransferred using an electromagnetic induction device, vision can beperceived with a natural feeling.

[0074] Moreover, the secondary coil 12 can be mounted in the ciliaryfurrow K or the crystalline capsule H. Compared with a case where thesecondary coil 12 is placed on the equatorial plane of the eyeball M,the primary coil 10 and the secondary coil 12 are located close to eachother. The efficiency in electromagnetic induction between the coils 10and 12 can be improved.

[0075] Moreover, the components other than the electrodes 11, that is,the integrated circuit 16 including the signal processing circuit, thesecondary coil 12, and the light receiving element 14 are mounted on andintegrated to the same substrate, and formed to have an appropriatesize. Therefore, the components can be implanted in the ciliary furrow Kor the crystalline capsule H. Consequently, compared with a case wherethe components are placed on the eyeball M, the implantation is easy todo. The damage to a user caused by the implantation is limited.

[0076] When a user wearing the artificial eye system 1 moves his/hereyeballs, the secondary coils 12 may tilt. Consequently, the efficiencyin electromagnetic induction between each pair of the primary coils 10and the secondary coils 12 may deteriorate, and electromotive forceinduced in the secondary coil 12 may decrease. Even in this case, sincepower in the power storage element 17 can be used, a stable image signalcan be transmitted to the retina N.

[0077] Moreover, the power storage element 17 can be implanted in theciliary furrow K or the crystalline capsule H. Therefore, compared witha case where the power storage element is placed on the eyeball M, theimplantation is easy to do. The damage to a user caused by theimplantation is limited.

[0078] Moreover, since the electrode unit 19 has a plurality of pores20, nutrition can be supplied from the cells of the sclera J to thecells of the retina N. Therefore, the electrode unit can be implantedunder the retina. Compared with a case where the electrode unit ismounted on the retina, the power of a signal to be transmitted to theretina N can be lowered. Consequently, even when the secondary coil 12is small and induced electromotive force is limited, a satisfactoryelectric stimulus signal can be transmitted to the retina N.

[0079] Moreover, the eye-gaze point recognizing units 13 are provided sothat an image acquired in the direction of the eye-gaze point recognizedby these units 13 is transmitted to the retina N, which achieves theartificial eye system 1 with excellent usability.

[0080] Moreover, the component for changing images with the movement ofthe eye-gaze point is not hardware (for example, not a component fordriving a light receiving element) but software. This results in asimple overall configuration.

[0081] <Other Embodiment>

[0082] Next, referring to FIG. 11, other embodiment will be described.The same reference numerals will be assigned to components identical tothose of the above embodiment, and the description of those componentsare omitted. In this embodiment, the outer diameter of a secondary coil30 is determined to be approx. 11 mm. The secondary coil 30 is placed inthe ciliary furrow K. According to the present embodiment, the outerdiameter of the secondary coil 30 is larger than that of the secondarycoil 12, which leads to the improvement in the efficiency ofelectromagnetic induction. Depending on a user, his/her lens andcrystalline capsule H may be entirely enucleated. In this case, as shownin FIG. 12, the secondary coil 30 is mounted in (stitched to) theciliary furrow K. Since the outer diameter of the secondary coil 30ranges from approx. 8 mm to approx. 12 mm (more preferably, from approx.9 mm to approx. 11 mm), the intracorporeal unit 3 can be mounted in aperson who has the crystalline lens and the crystalline capsule H of oneeye enucleated.

INDUSTRIAL APPLICABILITY

[0083] As described above, according to the present invention, there isprovided an artificial eye system which has excellent usability and ispractically feasible.

1. An artificial eye system in which stimulus signal producing means converts an image signal, which represents an image of an outside world received by an image receiving element, into an electric stimulus signal, and the electric stimulus signal is transmitted from an electrode attached to a retina, the system including: an extracorporeal unit which is mounted outside a user's body; and an intracorporeal unit which is mounted inside the user's body, wherein the extracorporeal unit includes a visor and a power supply unit which supplies electricity to the visor, the visor includes a primary coil, the image receiving element, and a light emitting element which transmits the image signal from the image receiving element as an imaging signal, and the intracorporeal unit includes: a secondary coil which is electro-magnetically induced by the primary coil; a light receiving element which receives the imaging signal from the light emitting element; a signal processing circuit which processes the imaging signal received by the light receiving element; and an electrode unit which has a plurality of electrodes that transmits the electric stimulus signal, which is processed by the signal processing circuit, to the retina.
 2. The artificial eye system according to claim 1, wherein an outer diameter of the secondary coil ranges approximately 5 mm to approximately 12 mm.
 3. The artificial eye system according to claim 1 or 2, wherein the signal processing circuit is integrated together with the electrodes on a substrate, and the outer diameters of the secondary coil and the light receiving element range from approx. 5 mm to approx. 12 mm.
 4. The artificial eye system according to claim 1, wherein the outer diameters of the signal processing circuit, the secondary coil, and the light receiving element range from approx. 5 mm to approx. 12 mm.
 5. An artificial eye system in which stimulus signal producing means converts an image signal, which represents an image of an outside world received by an image receiving element, into an electric stimulus signal, and the electric stimulus signal is transmitted from an electrode attached to a retina, the system including: an extracorporeal unit which is mounted outside a user's body; and an intracorporeal unit which is mounted inside the user's body, wherein the extracorporeal unit includes a visor and a power supply unit which supplies electricity to the visor, the visor includes a power transmitter which transmits power, the image receiving element, and an imaging signal transmitter which transmits the image signal from the image receiving element as an imaging signal, and the intracorporeal unit includes: a power receiver which receives the power from the power transmitter; an imaging signal receiver which receives the imaging signal from the imaging signal transmitter; a signal processing circuit which processes the imaging signal received by the imaging signal receiver; an electrode unit which has a plurality of electrodes that transmits the electric stimulus signal processed by the signal processing circuit to the retina; and a power storage element which supplies the power to the electrodes and the signal processing circuit.
 6. An artificial eye system in which stimulus signal producing means converts an image signal, which represents an image of an outside world received by an image receiving element, into an electric stimulus signal, and the electric stimulus signal is transmitted from an electrode attached to a retina, the system including: an extracorporeal unit which is mounted outside a user's body; and an intracorporeal unit which is mounted inside the user's body, wherein the extracorporeal unit includes a visor and a power supply unit which supplies electricity to the visor, the visor includes a power transmitter which transmits power, the image receiving element, an imaging signal transmitter which transmits the image signal from the image receiving element as an imaging signal, and an eye-gaze point recognizing unit which recognizes an eye-gaze point, the intracorporeal unit includes: a power receiver which receives the power from the power transmitter; an imaging signal receiver which receives the imaging signal from the imaging signal transmitter; a signal processing circuit which processes the imaging signal received by the imaging signal receiver to produce the electric stimulus signal for stimulating the retina; and an electrode unit which has a plurality of electrodes that transmits the imaging signal, which has been processed by the signal processing circuit, to the retina, and the electric stimulus signal representing information acquired in a direction of the eye-gaze point recognized by the eye-gaze point recognizing unit being transmitted from the electrodes to the retina.
 7. The artificial eye system according to claim 6, wherein an image receiving visual field whose image is represented by the image signal produced by the image receiving element is set to be larger than a transmitting visual field whose image is transmitted from the electrodes to the retina, and an image of a portion of the image receiving visual field located in the direction of the eye-gaze point recognized by the eye-gaze point recognizing unit is transmitted as an image of the transmitting visual field to the electrodes.
 8. The artificial eye system according to any one of claims 1 through 7, wherein the electrode unit has a plurality of pores formed penetrating through the electrode unit in a direction of a thickness. 